This invention relates generally to steering columns and more particularly to a steering column having improved locking, release and energy absorption mechanisms.
Various locking mechanisms are known for use with steering columns capable of rake adjustment, such as that disclosed in co-pending U.S. patent application Ser. No. 09/664,032 dated Sep. 18, 2000, which is incorporated herein by reference. The locking mechanism in that co-pending application includes a rake bolt and associated tooth locks on both sides of the steering column. It would be desirable from the standpoint of both simplicity and cost, for the locking mechanism to have a single tooth lock on only one side of the steering column.
It is also known to provide a release mechanism to allow the steering column to collapse following a frontal impact event of great magnitude, such as a head-on collision. However, such release mechanisms typically are not aligned with the rake bolt and thus lead to undesirable moments being applied to the release mechanism upon impact.
Energy absorption mechanisms that allow the steering column to collapse at a controlled rate for the protection of the driver are also known. Such mechanisms, however, typically are not well integrated with the rake adjustment and release mechanisms.
The locking system of the present invention includes a tooth lock movable selectively into engagement with a toothed slot of a fixed bracket. The tooth lock is normally supported in meshing engagement with the toothed slot to lock the steering column in adjusted position, but is movable out of engagement with the toothed slot to enable the steering column to be adjusted. A rake bolt moves into positive engagement with the tooth lock to hold the tooth lock in meshing engagement with the toothed slot in response to an applied impact force on the steering column to prevent the steering column from accidentally moving away from adjusted position during controlled collapse of the steering column.
Further in accordance with the invention, the steering column has telescoping upper and lower jackets. The rake bolt extends through a tubular capsule. The capsule is connected to a compression bracket secured to the upper jacket by one or more shear pins. The shear pin or pins are adapted to shear to enable the steering column to collapse when the driver""s chest hits the steering wheel in response to a frontal vehicle impact of great magnitude. A deformable energy absorbing strap extends over the capsule which serves as an anvil to bend and then restraighten the strap to absorb energy as the steering column collapses.